Systemically administered glioblastoma (GBM) therapeutics reach the brain in very low concentrations due to the presence of both the blood brain barrier (BBB) and the nanoporous electrostatically charged extracellular matrix, denoted here as the brain-tissue barrier. New delivery strategies, capable of providing higher local concentrations and more uniform dispersion in the brain, are critically needed. This need extends to the delivery of agents designed to inhibit or restore the expression of recently identified master regulatory miRNAs. These miRNAs regulate multiple oncogenic and tumor suppressive pathways in GBM, and therefore represent promising new targets for therapy. To achieve this goal, we will implement innovative miRNA and anti-miRNA delivery approaches that couple magnetic resonance image (MRI)-guided BBB opening via focused ultrasound (FUS) and microbubbles (MBs) with miRNA-expression modifying nanoparticles (BPN) that have been engineered to rapidly penetrate the brain-tissue barrier. The collaborative efforts of Co-PIs Price and Hanes have generated ample pilot data supporting our concept for miRNA/anti-miRNA BPN delivery. Our central hypothesis is that therapeutic molecules designed to modify the expression of master regulatory miRNAs will exhibit markedly enhanced efficacy when they are packaged in BPN and delivered to GBM with MRI-guided FUS and MBs. This proposal consists of 3 specific aims. Aim 1 will be to engineer BPN that effectively modify master regulatory miRNA expression in intracranial GBM xenografts in mice. BPN comprised of various core polymers will be fabricated using previously determined surface PEG chemistries. The ability of these therapeutic BPN to penetrate brain tumor tissue, as well as inhibit oncogenic miRNAs and/or restore tumor-suppressive miRNAs identified by Co-Investigators Abounader and Purow, will be tested. BPN with the most promising characteristics will be advanced to experimental therapeutic testing in Aim 3. Meanwhile, Aim 2 will be to develop MRI-guided approaches for the safe and effective delivery of these miRNA BPN to GBM using FUS and MBs. We will define FUS pressure thresholds for safe and reversible BBB opening and use them as boundaries in determining effective FUS and MB parameters for delivering BPN formulations. Studies for Aim 3 will first determine maximum tolerated dose and the pharmacokinetic profile of candidate miRNA/anti-miRNA BPN formulations. Next, the experimental therapeutic efficacy achieved by delivering miRNA/anti-miRNA BPN via MR-guided FUS and MBs will be examined. Controls will include non-penetrating nanoparticles and intravenously injected miRNA BPN formulations without FUS-mediated delivery. Efficacy will also be compared to that achieved using an established, yet highly invasive, convective enhanced delivery approach. Once completed, we believe these findings will establish miRNAs/anti-miRNA BPN as effective GBM therapeutics when delivered across the BBB using MRI-guided FUS and MBs.